The concentration of IgA, IgG, IgM, a1-antitrypsin, haptoglobin and transferrin was determined by the kinetic nephelometric method (Beckman immunochemistry analyzer) and by the radial immunodiffusion method (Behring partigen immunodiffusion plates). The investigation was carried out in 151 normal and pathological sera. The results obtained with the radial immunodiffusion method were for IgA, IgG and IgM in middle about 15%, for a1-antitrypsin about 50% and for haptoglobin about 80% higher as compared to the results determined with the kinetic nephelometric method. An acceptable correspondence between the two methods was found for the results of transferrin.